This invention relates to improvements on a button-type air cell, and more particularly to improvements on an air cathode.
The prior art air cell comprises liquid electrolyte and an air cathode prepared by mixing powdered or granular active carbon particles with a water-repellent binder such as powder of Teflon and compressing the mixture into a thin sheet while being carried by a conductive holder such as a nickel net.
The conventional air cell of the above-mentioned type had the drawbacks that the electrolyte pervaded the air cathode due to capillarity during long storage or long period discharge at an extremely small current to thickly cover the surface of the active carbon particles used as one component of the air cathode, thereby prominently decreasing the surface area of the active carbon which could be contacted by air with a decline in the oxygen-reducing power, discharge area and consequently discharge voltage.
The known process of eliminating the above-mentioned difficulties is to add a catalyst such as silver, palladium or platinum to the components of the air cathode, thereby sustaining the oxygen-reducing power of the air cell. However, any of these catalysts is expensive and has to be applied in a large amount, resulting in the high cost of an air cell produced.